Final answer:
Grade II is the grade of strain where the gap between the muscle fibers can be felt.
Step-by-step explanation:
The grade of strain where the gap between the muscle fibers can be felt is Grade II.
A muscle strain is an injury in which muscle fibers tear as a result of overstretching. Depending on the degree of injury to muscle fibers, a strain can range from mildly to extremely painful. In Grade II strains, there is partial tearing of the muscle fibers, which creates a noticeable gap between the fibers that can be felt when pressed.